An improved process for the preparation of purines

Abstract

The present invention relates to a process for the preparation of Purines. More particularly it relates to the preparation of Purines of formula (1) wherein X is hydrogen, thioaryl; R 1 and R 2 are hydrogen or acetyl.

1 . Purines of general formula (1)  
     
       
         
         
             
             
         
       
       wherein X is hydrogen, thioaryl; R 1  and R 2  are hydrogen or acetyl.  
     
   
   
       2 . A process for the preparation of purines of formula (1), the said process comprises the steps of; 
 (a) reacting an aminopurine derivative of formula (2),                          wherein X is 4-methylphenylthio, 4-chlorophenylthio with a triester of formula (4)                          wherein Q is leaving group and R is C 1-6  alkyl preferably methyl or ethyl group, in presence of an organic solvent under constant agitation at about 50° C. for a period of 2 to 5 hrs. to obtain an intermediate derivative of formula (5)                          wherein X is 4-methylphenylthio, 4-chlorophenylthio and R is C 1-6  alkyl preferably methyl or ethyl group;    (b) cooling the reaction mixture to a temperature at about 15° C. to obtain the solid intermediate derivative of formula (5);    (f) treating the compound of formula (5) with an alkoxide base in an alcoholic solvent at ambient temperature to obtain a diester;    (g) reducing and acylating the diester in situ to obtain the intermediate compound of formula (6), and                          (h) desulfurising the intermediate of formula (6) with Raney nickel to obtain the compound of formula (1).                          
   
   
       3 . A process as claimed in  claim 2 , wherein the organic solvent for preparing compound of formula (2) and washing of compound of formula (4) is alcohol.  
   
   
       4 . A process as claimed in  claim 3 , wherein the alcohols are methyl and ethyl alcohol.  
   
   
       5 . A process as claimed in  claim 2 , wherein in step (c) the alkoxide base is alkoxide base of alkali metals preferably sodium alkoxide.  
   
   
       6 . A process as claimed in  claim 2 , wherein preparation of 6-thioderivative is carried out by reacting 2-Amino-6-chloropurine with arylthiol in an alcoholic solvent and an organic base over a temperature range of 0° C. to boiling point of solvent preferably 25-30° C.  
   
   
       7 . A process as claimed in  claim 2 , wherein the organic bases used for the preparation of 2-Amino-6-chloropurine is selected from the group comprising of triethylamine, ethyldiisopropylamine, DBU in an alcoholic solvents.  
   
   
       8 . A process as claimed in  claim 7 , wherein the alcoholic solvent is selected from the group comprising of methanol, ethanol and isopropanol.